Thanks for bringing this topic, @prich88-googlema.
Changing your client's details in QuickBooks Self-Employed is only available each time you create an invoice, like what you did.
I've added some screenshots for your additional reference:
You may consider checking this article to help you with your future tasks: QuickBooks Self-Employed Self-Help Articles.
I'll be here if you have other questions. You can always tag my name in the comment section and I'll help you in any way I can. Take care.